Abstract
Interactions between the habitat structure and physical and chemical parameters generate environmental conditions that influence the distribution and abundance of macroinvertebrate species and their assemblages. This study describes the habitat structure and its effects on macroinvertebrate composition in an intermittent stream in the Brazilian semi-arid. Collections of benthic invertebrates were performed in three reaches along the Ipanema River during the dry and wet seasons using a “D” shaped net (40 cm wide and 250 μm mesh). A total of 23 taxa was recorded, Insecta being the most representative with 12 families and an average density of 168.1 ind/m². Correlations between environmental variables and CCA axes showed that substrate composition (sand and mud), macrophytes, litter and altitude were the main variables explaining benthic macroinvertebrate composition in the study stream. Canonical correlations between macroinvertebrate and physical and chemical variables were not significant. This study shows that the habitat structure contributes to the persistence and stability of macroinvertebrate communities in a Brazilian semi-arid stream, by creating refugia for organisms and contributing to the physical structures available for colonization. Key words: hydrological disturbances, patch dynamics, drylands.
Highlights
Drylands are usually associated with high and variable degrees of aridity, which are a reflection of low precipitation and high evapotranspiration
This study describes the structure of the habitat and physical and chemical variables along an intermittent river of the semi-arid region of Brazil
The Ipanema River showed an intermittent hydrological regime characterized by a wet phase with surface water flow in April and June and a dry phase in October and January, when flow was absent and pools were formed in the river bed (Figure 2)
Summary
Drylands are usually associated with high and variable degrees of aridity, which are a reflection of low precipitation and high evapotranspiration. The hydrological regime plays a major role on the organization of aquatic systems and their communities in drylands, by structuring the spatial distribution of organisms (Sheldon et al, 2002), enhancing diversity of species (Maltchik and Medeiros, 2006) and creating habitat variability (Mugodo et al, 2006) This is achieved as a result of flooding events that connect habitats previously isolated during the dry season and dry periods that spatially segregate the physical characteristics of the environment (Marshall et al, 2006). In Brazil, the extremes of drought and flooding are regarded as the main agents structuring the physical and biological systems in semi-arid streams, conditioning the river morphology, physical and chemical characteristics of the water and enhancing habitat heterogeneity (Maltchik and Florin, 2002; Medeiros et al, 2008) The interaction of these factors creates and maintains heterogeneous systems that segregate the abundance and distribution of species at different spatial scales and the community composition (see Medeiros et al, 2011; Maddock, 1999). The characteristics of the habitat and their spatial variation are thought to have important effects on the structure and organization of biological communities in semi-arid streams
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